Major emphasis is placed on the development and application of the scanning electron microscope and an associated energy dispersive X-ray (EDX) system to viral oncology studies. Immunological tagging with heavy metals and immunolatex spheres reacted to specific areas of the cell surface have been studied to provide a system for the localization of viral antigenic sites as detected by SEM-(EDX). The SEM and transmission electronmicroscope (TEM) were utilized to study the ultrastructural characteristics of human normal and tumor cells and two retraviruses: equine infectious anemia virus (EIAV) and bovine leukemia virus (BLV). The TEM-equipped with a video image intensification system has been utilized to study thin sections of virus pellets in order to obtain video tape stored information for pattern recognition studies.